Memories Never Really Leave
by live4fiction
Summary: "I killed everyone and I couldn't stop myself. There wasn't anyone left and then...I was dying." "(Y/n), that isn't you. Papyrus is alright, he's here. Everyone is alive and ok, because you are no killer." Reader has a nightmare about the genocide timeline so Sans is there to help. I don't own Undertale (Toby Fox does) or You (You own you).


**Sans x Reader**

Trigger Warning for Nightmares and Blood...As well as terrible puns ;)

(Reader's POV)

Every night the same hell... Every night I get to watch the friends I love die by my own hand... Every night, I watch my lover kill me... Some nights aren't as bad but tonight, tonight I got to watch the worst of my torment.

 _I watched as my body moved on it's own. I had no control over anything I did and I couldn't talk, or even scream. I watched as my body went to every home in Snowdin, killing the people inside. I tried to scream as my body shambled its way to Sans and Papyrus' home. I hoped and prayed that they weren't home, but I was mistaken when Papyrus opened the door. I cried and screamed as the knife shot through Papyrus' spine and shuddered when he turned to dust. The look in his eyes ripping off a piece of my heart._

 _I cowered and cried, trying to scream as I watch my body shamble all over the underground. I had to watch as Undyne, Alyphs, Mettaton, Napstablook, Asgore, Toriel, every monster die by my bloody knife, and a piece of my heart with all of their demises. After almost all of the underground was gone, all that was left of my heart was a small piece of red, cracked and barely staying together. The scene shifted and I was now in my own body again but I was in a great deal of pain, and standing above me was Sans, tears dripping from his eye sockets._

 _"You!" Sans growls above me as I lay on the ground, blood pouring from my chest. He lifts me by my throat, slamming me into a pillar. His hands were cutting off the precious supply of oxygen to my lungs and this was evident from the shallow gasps coming from my mouth. "Why'd you do it? You killed...all of them..." He growls, his left eye burning with blue fire but his hatred burning brighter. He looked sad for a short moment, but his hate was back soon after. He dropped me on the tile floor, my head making a loud thud. He lifted his hand above my face before using his magic to throw my body around, hitting everything nearby. "Die you bitch...you dirty brother killer," He growls before squeezing his hand into a fist, my body crushed along with it. I watched in horror and regret as my soul, broken and cracked, shattered on the floor, before disappearing into dust._

(Sans POV)

I'm worried about (y/n). For the past month or two, she's hasn't been her normal happy self and I don't know why. We've been dating for 2 years and I know when something's 'a-foot'. I went downstairs earlier to think since I didn't want to disturb her sleep with my 'bonehead'. I was getting some ketchup from the fridge (and laughing a little at my own puns) when I heard shuffling from my room, which isn't as bad as Pap says it is...at least since (y/n) started to sleep over. I walk up the stairs and unlock my door but I wish I didn't have to see what I did. (Y/n) was crying out and moving in her sleep, tears streaming down her face. She looked like she was clutching her heart and I could feel mine break.

I walked quickly over to the bed and stroke her cheek. "(Y/n)," I whisper, hoping she will calm down. Seeing no response, I shake her slightly, "(Y/n), (y/n) wake up." I say, getting a little louder so I can be heard. She's still doesn't notice me... ha, I guess she has a thick skull. I was about to try one more time when she shoots up, cold sweat dripping down her face and her teary eyes darting around the room. "Woah, calm down," I try and talk to her, reaching out to rub her head but she screams.

She scrambles to the corner of my room, curling up with her head between her knees and her hands on her head. "P-p-lease... please don't h-hurt me... I'm s-sorry... I'm so so sorry," She cries as my eyes widen. This was a really bad nightmare then. I slowly move towards her, hands forward so she won't get scared. "It's me. It's Sans. I won't hurt you (y/n), I promise," I whisper, now kneeling in front of her. She looks up at me with tear filled eyes and I force a smile, trying to calm her down the only way I know. "Knock knock?" I say, hoping she'd answer. I wait for a little and, not hearing an answer, continue with the joke. "Patella," I say, going to speak again when I hear a small voice. "Patella who?"

"Patella me what's wrong." I smirk, but it only lasts a little before concern is seen on my face. She laughs, if only a small bit, before tears flow from her eyes and she wraps her arms around my neck and cries into my shoulder. I put my arms around her, rubbing her back calmly whispering, "It's alright, it's alright. It was just a dream. I'm here, I'm here."

(Y/n) kept crying into my shoulder and I heard her mumbling what I assumed were more apologies. She calms down a small bit, but tears still fall from her eyes. I pull away a small bit to wipe away the tears with my thumbs. "Do you want to talk about it?" I ask her, not wanting to push her. She nods slightly, her breathing labored and soft.

"I...I couldn't do anything to stop it. I-I tried, I tried but..." She whimpered, more tears coming. "I killed everyone, and I couldn't stop myself..." My eyes went wide but I didn't let her see how shocked I was. I rubbed her back more, silently telling her it was alright to continue. "T-there wasn't a-anyone left and...then I was dying," She said, whispering out the last part. Now my eyes were closed, guessing what happened next. "Y-you were there and y-you...y-you..." She burst into tears again, scared from the mere mention of the nightmare.

I knew for a fact what she was talking about now and I couldn't apologize enough for those timelines to have entered her dreams. I hug her tightly, not planning on letting her go. She continued with her nightmare and I swore that, after what she said, I would treat her well, in every timeline. "Y-you were standing over me and started to choke me. I-I was already stabbed, b-but you l-looked like you wanted to kill me with your h-hands... You used your magic to throw me around before s-squeezing the life out of t-this... dirty brother killer..." She finishes, balling her fists at the last part.

My own hand were shaking, thinking back to that timeline...and all the other ones before that. That one was the last route before this one and it was the worst because I had given up on you. I thought the real you wasn't coming back, but then you did... I remember all the ways I had killed you before and that caused my own nightmares, but normally you were the one to keep them at bay. Now, here you are, scared to death and I can't even seem to help you. Even though tears were close to coming from my eye sockets, I grabbed your shoulders and made you look at me.

"(y/n), that isn't you. Papyrus is alright, he's here. Everyone is alive and ok, because you are no killer," I tell you, watching as you calm down slightly. I pull you closer and place a gentle "kiss" on your forehead, hugging you close to me. Quieter than you can hear, I whisper with tears slowly sliding down my face, "I won't ever do that to you again. I promise. It hurt so much to do that to you and I don't plan on you dying anytime soon. You have no idea how sorry I am..." I pick you up in my arms, and bring you back to my bed. I lay you down and get in next to you and cuddle you closely, using magic to bring up the covers.

"I love you (y/n). If this is why you haven't been happy recently, I will help you with the nightmares from now on," I murmur, feeling your breath get quiet and your heartbeat slow. "Sweet dreams kiddo, see you tomorrow."


End file.
